Method of making lead arseniate.



Patten opmg,

CLARENCE B. SPRAGUE, 0F SALT LAKE CITY, UTAH, ASSIGNOR 'lO UNITED STATES SMELTING, REFINING & MINING COMPANY, OF PORTLAND, MAINE, A CORPORA- TION 0F MAINE.

No Drawing.

Specification 01 Letters Eatent.

Application filed November 11, 1909. Serial No. 527,535.

METHOD MAKING LEAD ARSENIATE.

Patented June 11.0, i9 i3.

To all to/mm it may eonccm lle it known that I, Cmnnncu B. Srnaoun, a citizen of the United States, residing at Salt Lake City, in the'county of Salt Lake and State of Utah, have invented certain new and useful Improvements in Methods of l\ [aking Lead Arseniate; and Ido hereby declare the following to be a full, clear, and exact description oi the invention, such as will enable others skilled in the art to which it appcrtains to make and use the same.

The present invention relates to an im proved method of making lead arseniate.

Lead arseniate is in extensive and growing use as an exterminator of insects destructive to plant life.

In the wet way, it has been manufactured by a variety of methods, such as by the 0x1- 1 dation of arsenious acid to arsenic acid by methods in use, in that the lead arseniate is.

produced in the dry way, directly from the union of its elements, on the roasting of ma terials containing lead and arsenic in intimate association, in presence of air; and in the recovery of the lead arseniate so produced (which may be in admixture with other substances) which consists in dissolving it in a solution of an alkali hydrate and a/ftervard precipitating itby neutralizing the alkali with an acid.

I have discovered that on properly roasting materials containing lead and arsenic in presence of air, a reaction takes place resulting in the formation of lead arseniate. The arsenic and lead need not be present in the proportions in which they combine. If there is present an excess of arsenic over that. amount capable of uniting wit-h the lead-,this excess is expelled more or less comobtained as lead arseniate.

pletely as arscnious acid. If there is pres cut an excess of lead, this is left in the roast. as oxid or in some other form. It, in the. material to be roasted, the leiidand arsenic are present in the proper propel tions, practically thewhole of these may be i have also discovered that the lead arseniate so produccr'l is soluble in solutions of sodium and potassium hydrates; and that upon neutralizing the alkali with. acetic or nitric acid, the.

whole of the lead arseniate is precipitated from its solution.

Broadly stated, the process consists in the roasting of materials containing lead and arsenic, in presence of air with the fornnv tion of lead arseniate; the dissolving ot the lead arseniate so produced in a solution of caustic soda or potash; and, after filtration from any residue, the precipitation of the lead arscniate by neutralization of the alkali with acetic or nitric acid.

One specific application of the process contemplates the manufacture of lead arseniate from speiss and litharge; the former being an arsenic bearing material resulting from furnace operations, and the latter oxid of lead. For the purpose of making lead ar seniate, the spciss.is ground to a suitable fineness, and intimately mixed with the req uisite amount of litharge. For each pound of arsenic in the speiss 4:5 lhs. of litharge are used, and about 6 lbs. of lead arseniate' are produced. y

The roasting is conducted with access of air at a moderate red heat in a furnace of suitable construction, such as an ordinary revcrhcratory roaster, until the oxidation is complete. This may require, according to circlunstauces, (3 to 10 hours. The roast is next conveyed to leaching kcttlesand ex-' tractcd with a hot strong solution of caustic soda. say one containing 25 to 30 ieiucent. sodium hydrate. About 1.5 lbs. oi. caustic soda are used per pound of lead arseniate.

prcsent. After leaching out the lead at: seniate the solution is filtered from the insoluble residue and the alkali is neutralized with acetic 'or nitric acid. This'results in the precipitation of the lead arseninte which is filtered and washed and is'now ready for. use. .\bout 1.5 lbs. of acid are used. for

each peun i 0f caustic soda present in the soliiiie 'lhe acid may be regeneratefi by any appropriate methecl.

Having iiius described the invention what is claimed is:

The method ei making lead arseniate which consists in roasting at a moderate red heat with access ef air materials containing lead and arsenic, dissolving the lead arseniate in a solution of caustic alkali, and precipi- 10 tating the lead arseniate from the solution by neutralization, substantiall as described.

CLARENCE B. PRAGUE. Witnesses: 4

R. H. B TI ERFIELQD, Jessm E. ALLEY. 

